The present invention relates to a connector for a fiber optic cable. More particularly, the invention relates to a new and improved fiber optic connector including a holder for holding a fiber optic cable and an optical fiber which provides for high resolution tuning of the holder and prevents adhesive from leaking into the shell of a fiber optic connector.
Fiber optic connectors are known which have means for preventing rotation of the fiber optic cable after positioning within a connector body during a termination procedure, such as described in U.S. Pat. No. 5,096,276 to Gerace et al. Such patents are adapted to a push-pull type connector having a plug housing including a shell, a keying position which allows the connector to remain in a fixed position upon insertion with a receptacle, and at least one reciprocating holder in the shell for holding an optical fiber. The optical fiber is connected to the reciprocating holder and is compatible within its load bearing portion with the load bearing portion anchored to the shell. The fiber is reciprocable together with the reciprocating holder and is reciprocable with respect to the shell and the load bearing portion.
It is also known to tune ferrules to provide for precise optical alignment, as shown in U.S. Pat. No. 4,738,508 to Palmquist. However, Palmquist does not teach tuning during a termination procedure. The Gerace et al. patent in particular, includes a collar having square or hexagonal profiles which prevent rotation of the holder when inserted into the shell of a connector. This invention, which has only limited positions in which the holder may be inserted into the connector, does not allow for precise concentric positioning of eccentrically manufactured ferrules and may not be precisely orientated, or tuned, to a degree sufficient to alleviate high insertion loss which occurs when a pair of abutting optical fibers are not concentric upon a common mating axis.
Increasingly, high performance connectors are required having insertion losses of less than 0.25 dB, such as angle polished ferrules and single mode applications. As a standard ferrule has a core diameter which is, for example, 128 microns and a common optical fiber diameter of 127 microns inserted therein, an optical fiber may be as much as 1/2 micron from the concentric axis. Further, the abutting optical fiber may also be as much as 1/2 micron off the concentric axis, equaling a total possible eccentricity of the optical fiber in the cores of each ferrule of 1 micron. In addition, the ferrule core may in and of itself have been manufactured off the concentric axis. Although spinning and cleaving a ferrule may make the core concentric, some ferrules such as ceramic ferrules cannot be spun and are manufactured eccentric to the mating axis. This eccentricity, if unadjusted, could possibly result in total signal loss. Thus, tuning of such fibers to optimize the position relative to the concentric axis could improve optical alignment by an order of magnitude.
Therefore, a useful device is needed in order to achieve precise tuning of the fiber during the termination procedure. Such a device is accomplished by the present invention. By this invention, a different system is provided for inserting the fiber optic cable holder into the connector in multiple orientations to allow tuning the holder for high resolution and low insertion loss.
Effective tuning may be achieved by having at least twelve different surfaces, twice as many as shown in Gerace et al., and preferably between twelve and thirty-two surfaces. The multi-faceted holder also prevents rotation of the holder within the connector body and allows for easy insertion. The present invention is well suited to single mode applications where low insertion loss and return loss are performance characteristics, which are both optimized via tuning the fiber to the concentric axis. The present invention is also well suited to ferrules which are angle polished and require complete ferrule alignment to limit insertion loss.
The Gerace et al. patent also discloses a holder having a sheath which is attached to the body of the holder through which the optical fiber and optical cable extends. Assembly of the connector involves positioning a fiber optic cable holder within a connector body. Adhesive is then deposited into the body. The adhesive may be injected by a syringe introduced into an end portion of the sheath which has been cut at an angle to provide an enlarged optical mouth. The rear of the sheath which protrudes from the end of the connector is later trimmed. The adhesive is deposited near the front end of the connector body adjacent the ferrule, distant from the rear end of the sheath. A stripped fiber optic cable is then passed through the interior cavity of a strain relief boot and through a holder including a sheath and body. The optical fiber is then securely inserted into a ferrule at the front of the cavity. The sheath prevents leaking of adhesive from the holder and prevents the adhesive from spreading into the spring and shell of the connector. Following the introduction of the adhesive into the holder, the optical fiber is pushed through the ferrule in so doing coating the optical fiber which resides within the ferrule with the adhesive, assuring the fiber is permanently bonded to the passageway through the ferrule. If strength members and external jacket accompany the optical fiber, the strength members can be secured by crimping them between the load bearing portion of the connector and a crimp sleeve. Excess fiber protruding beyond the ferrule tip is then cleaned and removed. After the adhesive has set, the ferrule tip with optical fiber is polished.
The Gerace et al. patent does not allow for manufacture of a one-piece body which prevents leaking of adhesive but is also easily installed and assembled. The present invention does not require trimming of the rear sheath, as it does not extend beyond the rear of the connector. By this invention, a different system is provided wherein the holder is a one-piece, integrally molded material including a rear body to prevent adhesive leakage, thereby avoiding adhesive on the spring which would prevent deflection of the ferrule upon mating.
By this invention, a fiber optic connector with a holder is provided which provides for high resolution tuning of the holder, is more easily inserted into a fiber optic connector, does not require assembly, does not require cutting at an angle, and has no chance of adhesive leaking into the body of the connector.
In order to overcome the deficiencies of the prior art compositions, it is an object of the present invention to provide a new and improved holder which allows concentric positioning of the fiber with respect to the common mating axis.
It is another object of the present invention to provide a new and improved holder which allows for more accurate tuning of the fiber to maximize resolution.
It is a further object of the present invention to provide a new and improved holder which is easily manufactured and assembled.
It is another object of the present invention to provide a new and improved holder which prevents the leaking of adhesive into the body of a fiber optic connector.
It is further object of the invention to avoid separation of the rear body from the holder body while tuning.
It is a another object of this invention to provide a new and improved holder which may be inserted in many positions and once inserted, prevents rotation of the holder.